The invention concerns a system for data display by means of magnetically controlled bistable rotors. Such systems are already known (French Pat. No. 79.17804). They include at least two rotors, each formed by a body having ranges of different colors in two diametrically opposite areas and which rotates freely in a mounting to which it is associated by a shaft.
A permanent magnet, the position of which is such that the line passing through its poles is essentially radial to the axis of the shaft, interlocks in rotation with this body.
To control the body's rotation, this magnet cooperates with one pole of an electromagnet connected to a source of direct current by an inverter-interruptor.
The operating principle of such a bistable element is simple.
A problem arises, however, when for example in order to be read at a very great distance the designation controlled by a single electromagnet must have a large surface, since each range able to achieve an elementary designation must itself be very broad.
In the designs known to date, the electromagnet generally acts on a simple rotor which, in order to carry this elementary designation, must provide opposing surfaces at least as large as those of said designation, and therefore, whether the rotor is cylindrical, spherical or flat, it requires a significant space, if only during its operation, which can only be reserved for it in very thick panels.
Furthermore, for its operation it requires an equally significant motor torque.
In order to limit these drawbacks, it is known (U.S. Pat. No. 3,924,226) that each elementary designation can be distributed over two contiguous rotors controlled synchronously by a common electromagnet.
In this known design, the electromagnet has its two poles spaced the same distance apart as the axes of the two rotors behind which they are placed so that each of them controls one of the rotors by repulsion of the identical pole and attraction of the opposite pole of the permanent magnet.
In this design, the pole of the permanent magnet identical to that of the electromagnet therefore remains free, and its repulsion and attaction force is therefore not exploited. This obviously results in a loss of power.
Furthermore, utilization of this electromagnet thus assembled is necessarily limited to the control of one rotor per pole and therefore of two rotors, which still often provides a surface too small to carry an elementary designation legible from afar.